the benefits of carpooling

UC BerkeleyRecent Work

TitleThe Benefits of Carpooling

Permalinkhttps://escholarship.org/uc/item/7jx6z631

AuthorsShaheen, Susan, PhDCohen, Adam, MCRPBayen, Alexandre, PhD

Publication Date2018-10-22

DOI10.7922/G2DZ06GF

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The Benefits of Carpooling

ABOUT THE AUTHORS

SUSAN SHAHEEN, PHD

Susan Shaheen is a pioneer and thought leader in future mobility strategies.

She was among the first to observe, research, and write about changing

dynamics in shared mobility and the likely scenarios through which

automated vehicles will gain prominence. She is an internationally

recognized expert in mobility and the sharing economy and co-directs the

Transportation Sustainability Research Center of the Institute of

Transportation Studies at the University of California, Berkeley. She is also

an adjunct professor in Civil and Environmental Engineering at UC Berkeley.

Her research projects on carsharing, smart parking, and older mobility have

received national awards. She received the 2017 Roy W. Crum award from

the Transportation Research Board for her distinguished achievements in

transportation research. In May 2016, she was named one of the top 10

academic thought leaders in transportation by the Eno Transportation

Foundation.

ADAM COHEN, MCRP

Adam Cohen a shared mobility researcher at the Transportation

Sustainability Research Center at the University of California, Berkeley.

Since joining the group in 2004, his research has focused on shared mobility,

mobility on demand, smartphone apps, and other transportation innovations.

He has coauthored numerous articles and reports on shared mobility in peer-

reviewed journals and conference proceedings. His academic background is

in city and regional planning and international affairs.

ALEXANDRE BAYEN, PHD

Alexandre Bayen is the Liao-Cho Professor of Engineering at UC Berkeley

and Director of the Institute of Transportation Studies (ITS). He is a Professor

of Electrical Engineering and Computer Science, and Civil and Environmental

Engineering. Prior to working at UC Berkeley, he was a visiting researcher at

NASA Ames Research Center and he worked at the Department of Defense

in France, where he holds the rank of Major. He has received numerous

awards, including the Ballhaus Award from Stanford University, of the

CAREER award from the National Science Foundation and he is a NASA

Top 10 Innovators on Water Sustainability. His projects Mobile Century and

Mobile Millennium received the Best of ITS Award for ‘Best Innovative

Practice’, at the ITS World Congress and a TRANNY Award from the

California Transportation Foundation. Bayen is the recipient of the

Presidential Early Career Award for Scientists and Engineers (PECASE)

award from the White House. He is also the recipient of the Okawa Research

Grant Award, the Ruberti Prize from the IEEE, and the Huber Prize from the

ASCE.

THIS WORK WAS PERFORMED BY THE AUTHORS AS INDEPENDENT CONSULTANTS. WE WOULD LIKE TO THANK GOOGLE FOR GENEROUSLY FUNDING THIS EFFORT. WE WOULD ALSO LIKE TO THANK LEW PRATSCH WHO PROVIDED VALUABLE INSIGHTS. ALL OPINIONS CONTAINED IN THIS REPORT REFLECT THE INDEPENDENT VIEWS AND ANALYSIS OF THE AUTHORS.

|1THE BENEFITS OF CARPOOLING The Environmental and Economic Value of Sharing a Ride

THE BENEFITS OF CARPOOLING |2 The Environmental and Economic Value of Sharing a Ride

THE BENEFITS OF

CARPOOLING THE ENVIRONMENTAL AND ECONOMIC VALUE OF SHARING A RIDE

CARPOOLING IS A DEMAND MANAGEMENTSTRATEGY THAT CAN REDUCE CONGESTION,

EMISSIONS, AND FOSSIL FUEL DEPENDENCY.

CONCLUSION 4

HOW GOVERNMENT

AND EMPLOYERS CAN

SUPPORT CARPOOLING

3

INNOVATIONS AND

TRENDS IN MOBILITY

2

CARPOOLING IMPACTS

AND MOTIVATORS 1 OVERVIEW

CARPOOLING IMPACTS AND MOTIVATORS

Carpooling allows travelers to share a ride to a common destination and can

include several forms of sharing a ride, such as casual carpooling and real-

time carpooling. Because carpooling reduces the number of automobiles

needed by travelers, it is often associated with numerous societal benefits

including: 1) reductions in energy consumption and emissions, 2) congestion

mitigation, and 3) reduced parking infrastructure demand.

INNOVATIONS AND TRENDS IN MOBILITY

In recent years, economic, environmental, and social forces coupled with

technological innovations are encouraging shared and pooled services.

Shared mobility is changing how people travel and is having a transformative

impact on mobility. This chapter reviews key trends impacting the mobility

marketplace including the growth of shared mobility and key demographic

indicators, such as an aging population and Millennials entering the workforce.

HOW GOVERNMENT AND EMPLOYERS CAN SUPPORT

CARPOOLING

For decades, carpooling has been used as a strategy by numerous public

agencies and employers as a strategy to address a range of climate,

environmental, and congestion mitigation goals, while simultaneously

increasing roadway and parking capacity. This chapter discusses how

employers and public agencies can support carpooling.

CONCLUSION

This chapter concludes with a summary of key findings from the report.


1

CARPOOLING IMPACTS AND

MOTIVATORS


WHAT IS CARPOOLING?

Carpooling allows travelers to share a ride to a common

destination. Carpooling can include several forms of

sharing a ride (Shaheen and Cohen, 2018a; Chan and

Shaheen, 2012; SAE International, 2018).

Common carpooling terms include:

▪ Casual Carpooling, also known as “slugging” and

“flexible carpooling” is a form of ad hoc, informal

carpooling among strangers. Typically, no money

exchanges hands or passengers pay a nominal

amount to reimburse drivers for actual travel

expenses, such as tolls, gas, etc. In some

regions, casual carpooling locations may be

designated where drivers can pick-up passengers

waiting for a shared ride.

▪ Real-Time Carpooling, also known as “app-based

carpooling” and “dynamic carpooling” allows

people to arrange ad hoc rides on-demand (or

very short notice) using smartphone apps or a

website. Typically, passengers are picked-up at

their current location or a mutually agreed upon

pick-up location.

▪ Vanpooling typically consists of 7 to 15

passengers sharing the cost of a van and may

share driving responsibility.

CARPOOLING DIFFERS FROM FOR-HIRE

VEHICLE SERVICES, SUCH AS RIDESOURCING,

RIDEHAILING, OR TRANSPORTATION NETWORK

COMPANIES (TNCS) IN ITS FINANCIAL

MOTIVATION. WHEN A CARPOOL PAYMENT IS

COLLECTED, IT PARTIALLY COVERS THE

DRIVER’S COST AND IS NOT INTENDED TO

RESULT IN A FINANCIAL GAIN. ADDITIONALLY,

THE DRIVER HAS A COMMON ORIGIN AND/OR

DESTINATION WITH THE PASSENGERS.

While taxis are often regulated to charge static fares, ridesourcing/TNCs often uses market-rate pricing, popularly known as “surge pricing” when prices usually go up during periods of high demand to incentivize more drivers to take ride requests. While some ridesourcing/TNC services offer shared rides for more than one traveler, these services are commonly referred to as “ridesplitting,” “pooling,” and “taxi sharing,” the latter used to describe sharing a taxi cab (SAE International, 2018). While a user may request a shared ride for a lower fare through a ridesplitting service, a pooled ride is not guaranteed.

CARPOOLING IS THE SECOND MOST COMMON

TRAVEL MODE TO WORK IN THE UNITED STATES

AFTER DRIVING ALONE. HOWEVER, TOTAL

PERCENTAGES HAVE DECLINED IN RECENT

DECADES. MORE POLICY SUPPORT IS NEEDED

TO REVERSE THIS TREND AND INCREASE

CARPOOLING MODAL SHARE, PARTICULARLY IN AN

AUTOMATED VEHICLE FUTURE.

FIGURE 1.1 U.S. CENSUS COMMUTING BY AUTOMOBILE: 1980 TO 2016

Source: U.S. Census Bureau, 2016


IMPACTS OF CARPOOLING

A number of social, environmental, and behavioral

impacts have been attributed to carpooling, and an

increasing body of empirical evidence supports many of

these relationships—although more research is needed

as carpooling is difficult for researchers to observe and

record. Empirical and anecdotal evidence indicates that

carpooling provides numerous societal benefits, such as:

1) reductions in energy consumption and emissions, 2)

congestion mitigation, and 3) reduced parking

infrastructure demand. Individually, carpooling users can

benefit from: 1) shared travel costs, 2) travel time

savings from high occupancy vehicle lanes, 3) reduced

commute stress, and 4) often preferential parking and

other incentives (Cohen and Shaheen 2016) (Chan and

Shaheen 2012). This chapter reviews three categories of

carpooling impacts: societal, employer, and individual

benefits.

SOCIETAL BENEFITS

Carpooling can provide numerous societal benefits, such as:

▪ Reduced vehicle miles traveled;

▪ Reductions in fuel consumption and greenhousegas (GHG) emissions;

▪ Reductions in adverse air pollution impacts onlow-income, minority, and other environmentaljustice populations; and

▪ Cost savings for public agencies and employers.

Each of these topics are discussed in greater detail in the sections that follow.

REDUCED VEHICLE MILES TRAVELED

(VMT)

Vehicle miles traveled (VMT) is a travel demand

metric that measures the sum of the number of miles

traveled by each vehicle. A study by the Federal

Highway Administration during the 1970s energy

crisis found a 23% reduction in vehicle miles traveled

(VMT) (Pratsch, 1979). Employee-based trip

reduction (EBTR) and transportation demand

management (TDM) programs are recognized as a

best practice to support VMT reduction goals.

However, many of these programs lack performance

monitoring and assessment and only a handful of

empirical studies have examined the VMT impacts of

these policies. One study found that employees

participating in the program had 4.2% to 4.8% lower

VMT than employees at the same worksite who did

not participate (Herzog et al., 2006). Studies

assessing the implementation of Washington State’s

Commute Trip Reduction Law have found similar

effects. Lagerberg et al. (1997) found an average

VMT reduction of 6% for employees at worksites

subject to the law. Boarnet et al. (2010) estimates that

these programs can reduce VMT for workplace

commutes by 4% to 6% (or approximately 1%

regionally).

Only two studies estimated VMT reduction for the

entire region or metropolitan area. Hillsman et al.

(2001) used survey data from employers to estimate

the number of commute trips eliminated by

Washington State’s commute trip reduction (CTR)

program. The study estimated declines in total VMT of

1.33% on all roadways and a reduction in freeway

VMT of 1.07% for the four central counties in

metropolitan Seattle. That is a smaller impact than

other studies because the authors examined all travel

during the morning peak including: commute trips to

non-participating sites and non-commute trips. A

separate study by the Commute Trip Reduction Task

Force using different years in the same data set

analyzed by Hillsman et al. (2001) estimated a 1.6%

reduction in total VMT (Commute Trip Reduction Task

Force, 2005).

It is important to note that carpooling could lead to

induced demand due to reduced travel times and

costs. So, this should be factored into calculations of

the net VMT impacts of this mode.

REDUCED FUEL CONSUMPTION

Every year, the average passenger car and sports utility

vehicle consumes an estimated 550 and 915 gallons of

fuel, respectively. Noland et al. (2006) assert that

enacting policies to increase carpooling is the most

effective strategy to reduce energy consumption besides

prohibiting driving. Another study by Jacobson and King

(2009) estimates a potential fuel savings of 0.80 to 0.82

billion gallons of gasoline per year in the United States, if

one additional passenger was added in every 100

vehicles. The same study also estimates a potential

annual fuel savings of 7.54 to 7.74 billion gallons per

year in the U.S., if one additional passenger was added

to every 10 vehicles.

Another study found that carpooling could save 33

million gallons of gasoline daily, if each average

commuting vehicle carried one additional passenger

(PACommutes, 2016). Regionally, carpooling can have a

notable impact on fuel savings as well. For example, in

the San Francisco Bay Area, a study estimated an

annual reduction of 450,000 to 900,000 gallons of

gasoline; the majority of this savings is attributable to


carpooling’s congestion reduction impact on the rest of

traffic (Minett and Pearce, 2011).

STUDIES HAVE FOUND THAT CARPOOLING

CAN SAVE FUEL AND REDUCE GREENHOUSE

GAS EMISSIONS FOR CARPOOLING USERS

AND NON-USERS, THE LATTER BY

REDUCING CONGESTION OF GENERAL

PURPOSE TRAFFIC.

REDUCED GREENHOUSE GAS (GHG)

EMISSIONS

By reducing fuel consumption, a number of studies

have found that carpooling can reduce greenhouse

gas (GHG) emissions. Using a simulation model,

Herzog et al. (2006) forecasts that individually

carpoolers reduce personal commute GHG emissions

by approximately 4% to 5% after joining an employer

trip reduction program. A study by Jacobson and King

(2009) estimates savings of 7.2 million tons of GHG

emissions annually in the U.S., if one additional

passenger were added to every 100 vehicles. The

study also estimates a savings of 68.0 million tons of

GHG emissions annually in the U.S., if one passenger

were added to every 10 vehicles (Jacobson and King

2009). In another study, the SMART 2020 report

estimates that employing information and

communication technology (ICT), such as app-based

carpooling to optimize roadway performance could

abate 70 to 190 million metric tons of carbon dioxide

emissions (Global e-Sustainability Initiative, 2008).

REDUCING TRAFFIC-RELATED EMISSIONS

FOR LOW-INCOME AND MINORITY

HOUSEHOLDS

Low-income and minority households commonly bear

disproportionate exposure to vehicular emissions

along congested roadways. Approximately 4% of

Americans (11.3 million people) live within 500 feet of

a major highway. Research indicates that certain

populations (e.g., members of minority communities,

foreign-born persons, and persons who speak a non-

English language at home) are likely to be at a higher

risk for exposure to traffic-related air pollution as a

result of residential proximity to major highways

(Schweitzer and Valenzuela, 2004; Downey et al.,

2008; Lopez, 2002; Morello-Frosch and Jesdale,

2006; Schweitzer and Zhou, 2010). Urban outdoor air

pollution is one of the top 10 causes of death in high-

income nations (World Health Organization 2013). As

such, carpooling can serve as one primary prevention

strategy to reduce traffic-related emissions to these

communities.

COST SAVINGS FOR PUBLIC AGENCIES

AND EMPLOYERS

By improving infrastructure capacity and person

throughput, carpooling is a cost-effective strategy to

mitigate congestion and reduce the need for

additional roadway and public transit capacity. In

Seattle, a Commute Trip Reduction Ordinance has

contributed to a 11% reduction in single-occupant

vehicle trips (City of Seattle, 2017). Another study found that casual carpooling has the potential to notably reduce energy consumption for 150 commuters equivalent to providing an express bus service implementation for the same number of commuters but at a lower cost (Dorinson et al., 2009).

EMPLOYER BENEFITS

Employers benefit from carpooling in a number of

ways. For employers, carpooling can:

▪ Reduce the need for parking;

▪ Increase the productivity and morale ofemployees; and

▪ Provide financial and tax benefits for employers.


REDUCED NEED FOR PARKING

By reducing the number of vehicle trips, public and

private sector employees can reduce parking demand

thereby saving capital costs of $15,000 to $45,000

USD per parking space (depending on design and

land availability) and operational costs of

approximately $360 to $2,000 USD annually per

parking space (Shoup, 2011; Environmental

Protection Agency, 2005).

INCREASED PRODUCTIVITY AND MORALE

Although research is limited, anecdotal evidence

suggests that employees who carpool may enjoy

reduced commute stress associated with driving and

increased convenience associated with high

occupancy vehicle (HOV) lane time savings and

preferential parking at their destination. These

benefits can in turn improve employee morale and

increase overall satisfaction and productivity.


FINANCIAL AND TAX BENEFITS

Carpooling provides a number of financial and tax

benefits to both employers and employees. Section

132(f) of the U.S. Internal Revenue Code provides a

way for employers to provide parking, public transit,

vanpool, and bicycle expenses on a tax-free

basis. The monthly cap for the parking, public transit,

and vanpool benefits are now at $260 USD/month

and are subject to annual cost of living increases.

Previously employers could deduct the subsidy

portion of a commuter’s expenses that were paid for

by the employer. This tax benefit was eliminated with

the passage of the Tax Cut and Jobs Act of 2017,

which removed this employer deduction. Employers

can still subsidize these expenses; however, they can

no longer deduct the subsidized portion of their

commuters’ expenses.

However, a number of states have implemented state

level commuter tax benefits and tax credits for

carpooling. For example, Maryland offers a tax credit

of 50% of the eligible costs of providing commuter

benefits. Employers and non-profits [501(c)(3) and

(4)] can claim a credit for 50% of the eligible costs up

to a maximum of $100 USD per employee per month.

The tax credit can be taken against state personal

income tax, corporate income tax, or the insurance

premium tax and is applicable to public transit

passes, employer vanpool programs, guaranteed ride

home programs, and parking cash out programs

(Comptroller of Maryland, 2018).

In Georgia, employers can receive an annual $25

USD tax credit for each employee that uses a federal

qualified transportation fringe benefit. To qualify,

employees must use the commute alternative at least

10 times per month. This credit is available to

employers that pay the Georgia corporate income tax

and provide public transit pass subsidies or vanpool

subsidies for employees or qualified carpool/vanpool

parking on or near the business premises (Georgia

Code 48-7-29.3).

Finally, in Washington state, employers and property

managers who are taxable and provide financial

incentives to their employees for carpooling (carrying

two or more passengers), carsharing, public

transportation, and non-motorized commuting before

January 1, 2024 are allowed a credit against taxes

payable or amounts paid to or on behalf of employees

up to $60 USD per employee per fiscal year. The

maximum eligible tax credit is $100,000 USD per

employer or property manager per fiscal year.

INDIVIDUAL BENEFITS & CARPOOL

MOTIVATORS

Studies suggest that carpooling is a flexible solution that is used by many user groups. Although research is limited, carpooling participants frequently benefit from carpooling in a number of ways. Common individual carpooling benefits and motivators include:

▪ Enhanced accessibility and economicopportunity for low-income households;

▪ Cost savings associated with shared travelcosts; and

▪ Increased convenience and reduced stress fromshared driving responsibilities and travel-timesavings associated with HOV lane access.


WHO USES CARPOOLING

Carpooling is a flexible solution that is used by many

users. A number of studies have found that casual

carpooling participants are more likely to be single or

married without children. Teal (1987) found that

carpool participants were more likely to have lower

incomes and be the second worker in a household.

Another study of casual carpooling users between the

ages of 25 and 34 in Houston found that they were

more likely to make commute trips (96%) versus non-

commute trips (80%) (Burris and Winn, 2006). This

study also found that HOV lane users tended to

belong to larger households with over 60% of

carpools comprising family members.

ENHANCING ACCESSIBILITY AND

ECONOMIC OPPORTUNITY FOR LOW-

INCOME AND MINORITY HOUSEHOLDS

In the nation’s largest metropolitan areas, 7.5 million

predominantly lower-income households do not have

access to an automobile (Tomer, 2016). Only 40% of

these public transit dependent households can

access metro-wide jobs with a commute of 90-

minutes or less (Tomer, 2016). Long commutes and

limited job access via public transportation in most

metropolitan regions leaves many jobs out of reach

for carless households.

Some studies have shown that carpooling can provide

job access to households with lower incomes and

households with more workers than vehicles (Teal,

1987). More recent data from the National Household

Travel Survey and the American Community Survey

show that ridesharing users tend to have lower

incomes, and Hispanics and African Americans

|8

carpool more than other racial and ethnic groups.

These surveys and other studies indicate that

ridesharing may serve an important role in enhancing

mobility in low-income, immigrant, and nonwhite

communities where travelers are more likely to be

unable to afford personal automobiles and obtain

drivers’ licenses (Liu and Painter, 2012).

COST SAVINGS

A number of studies have shown that some

carpooling users can have longer commute distances

and therefore have higher commute costs (Teal

1987). As such, carpooling can be an important cost

saving travel strategy for commuters. For example, in

the San Francisco Bay Area, commuters often use

casual carpooling to get from the East Bay to

downtown San Francisco during the morning

commute. Carpooling, which uses the HOV lanes of

the San Francisco-Oakland Bay Bridge, allows

travelers to take advantage of a toll discount and

shorter waits at the toll plaza. According to a 1998

survey, approximately 9,000 commuters (6,000 riders

and 3,000 drivers) used casual carpooling each

morning (Metropolitan Transportation Commission,

1999).

CONVENIENCE

Commuters who participate in carpooling frequently

have access to preferential parking and HOV lanes,

contributing to carpooling’s convenience and time

savings. Several casual carpooling studies have

documented travel time savings, cost savings, and

convenience as key motivators to share a ride

(Maltzman, 1987; Reno et al., 1989; Beroldo, 1990,

1999; Burris and Winn, 2006). One study of casual

carpooling in the San Francisco Bay Area found that

convenience, time savings, and monetary savings,

were key motivators to carpool (Shaheen, Chan, and

Gaynor, 2016).

Another study of casual carpooling in Washington

D.C. and Northern Virginia found that driver departure

flexibility was a primary reason for driving instead of

riding as a carpool participant. The study also found

that the top reason for choosing to be a rider was the

desire to save on the cost of gasoline, followed by a

preference to do other things during the drive

(Oliphant, 2008). This study found that 60% of casual

carpooling participants in Washington D.C. and

1 Shaheen et al. (2016) found that 75% of casual carpool users were former public transit riders compared to approximately 10% that previously drove alone. Casual carpooling competes with public transit due to reduced travel times (HOV lane access) and costs (typically much less expensive than comparable trips on public transit). Due to the potential for reduced travel times and costs, carpooling could encourage more people to drive, a phenomenon known as induced demand (Shewmake, 2018).

THE BENEFITS OF CARPOOLING The Environmental and Economic Value of Sharing a Ride

Northern Virginia only participated as passengers;

12% only participated as drivers; and 28%

participated as both passengers and drivers.

The inability to have access to a private vehicle during

the work day is often cited as a common drawback

associated with traditional carpooling and

ridematching programs. However, on-demand app-

based carpooling and a variety of shared modes are

converging to help overcome this challenge. Today

an increasing number of shared mobility options, such

as carsharing, bikesharing, scooter sharing, and

others are providing carpooling users innovative

options for getting around during the workday. On-

demand app-based carpooling services are also

providing increased flexibility. App-based carpooling

options can help address potential inconveniences

associated with traditional carpooling by allowing

carpoolers to have different morning and evening

carpool matches. This allows travelers to share a ride

who may not have been able to previously due to

variable or irregular work schedules.

SUMMARY

Carpooling can provide numerous societal, employer, and individual benefits including:

▪ Reducing VMT1, fuel consumption, and GHGemissions;

▪ Cost savings for public agencies and employers;

▪ Serving environmental justice communities byreducing the adverse impacts of air pollution andincreasing accessibility and mobility for low-income and minority households;

▪ Reducing the need for employer parking;

▪ Increasing the productivity and morale ofemployees;

▪ Providing financial and tax benefits foremployers;

▪ Reducing commute times, lowering commuterstress, and increasing convenience by sharingdriving tasks, accessing HOV lanes, and usingpreferential parking;

▪ Enhancing access, mobility, and economicopportunities for low-income and minoritycommunities who may be unable to afford avehicle; and

▪ Providing cost savings, tax benefits, and otherincentives for travelers that carpool.


2

INNOVATIONS AND TRENDS IN

MOBILITY



In recent years, socio-economic forces⎯coupled with

advancements in technology, social networking,

location-based services, wireless services, and cloud

technologies⎯are contributing to the growth of shared

and on-demand mobility, such as app-based carpooling.

Carpooling’s potential to reduce congestion, emissions,

and fossil fuel dependency is becoming a frequent topic

of discussion. This chapter discusses both innovations

and trends impacting mobility as well as other

considerations, such as the growth of megaregions, the

role of telework, attitudes toward driving, Millennials and

mobility, and suburbanization.

INNOVATIONS AND TRENDS

Technological, mobility, social, and demographic trends

are also changing the way people travel and carpool

(Shaheen et al., 2017; Martin et al., 2016). These include

technology, mobility, and demographic trends.

TECHNOLOGICAL TRENDS

▪ The growth of cloud computing, location-based

navigation services, and mobile technologies;

▪ The expansion of data availability, collection,

sharing, aggregation, and re-dissemination

through crowd-sourced private- and public-

sector sources facilitated through public-private

partnerships, application programing interfaces

(APIs), and other tools; and

▪ The commodification of passenger services

supporting app-based and on-demand

transportation options.

MOBILITY TRENDS

▪ Increasing demand and urban congestion,

reduced transportation funding, and the critical

need to maximize existing infrastructure

capacity;

▪ Growing popularity of shared and higher

occupancy modes, such as microtransit, app-

based carpooling, and others; and

▪ Increasing consumer interest in on-demand


SOCIAL TRENDS

▪ Heightened environmental awareness about

emissions and carbon footprints;

▪ Growth of megaregions as economic centers

and transportation corridors (Lang and Dhavale,

2005);

▪ Urbanization and reduced reliance on private

vehicle ownership; and

▪ Hyper-demand and the need for instant

gratification driven in part by growing

expectations for immediate results⎯enabled

and magnified by the mobile Internet and

smartphone apps⎯that create increasing

consumer desire for on-demand goods and

services, including mobility.

DEMOGRAPHIC TRENDS

▪ Demographic changes, such as rising life

expectancies, people working longer, and

Millennials entering the workforce;

▪ Persons with disabilities comprise nearly 20% of

the U.S. population;

▪ In 30 years, the U.S. population is expected to

grow by approximately 70 million people;

▪ By 2045, the number of Americans over the age

of 65 will increase by 77%;

▪ People are delaying life milestones, such as

getting married and having children that could

have an impact on automobile ownership and

use. For example, the average age of marriage

for men and women has increased from 23.2

and 20.8, respectively in 1970 to 29.2 and 27.1,

respectively in 2015 (U.S. Census Bureau,

2016); and

▪ A number of studies have documented that

Millennials are increasingly embracing apps and

other technologies (Shaheen et al., 2016);

Transportation Cooperative Research Program

2013; Transportation Research Board 2016;

Dutzik et al., 2014).

WHAT’S CHANGING, WHAT’S NOT

This section discusses other trends that could impact the

future of carpooling, including:

▪ Growth of Megaregions

▪ Role of Telework and Telecommuting

▪ Attitudes Toward Driving

▪ Millennials and Mobility

▪ Suburbanization.

These trends could have a notable impact on carpooling

in the future (Martin, Shaheen, and Zohdy, 2016;

Shaheen and Cohen, 2018b). For example, the growth

of megaregions could lead to the growth of “super

commuters” who works in one metropolitan area and

resides outside that urban area. Similarly, the growth of

telework and telecommuting could change how travelers

carpool. Rather than using pre-arranged ridematching


with the same carpool partner on a routine basis, flexible

work schedules and part-time telecommuting could result

in a growing number of flexible and on-demand

carpoolers. Finally attitudes toward driving, mobility, and

suburbanization among Millennials and the broader

workforce has notable implications on residential

location choice and key travel behavior indicators, such

as vehicle ownership and use. Continued suburban

growth could reinforce automobile dependency in many

metropolitan regions. Each of the following sections

discuss the ways in which these trends could impact the

future of carpooling.

DEVELOPMENT OF MEGAREGIONS

Interstate corridors have given rise to “megaregions,”

which could contribute to the growth of “super

commuters” who work in one metropolitan area and

reside outside that urban area. Megaregions are large

metropolitan areas that connect various separate urban,

suburban, and rural areas through shared economic,

social, and cultural ties (Figure 2.1) (America, 2050). In

some cases, a megaregion may be comprised of several

growth centers of growth that are more closely

interlinked to each other than they are to other regions of

the United States. Lang and Dhavale (2005) estimate

that ten regions in the U.S. will have populations

exceeding 10 million residents by 2040. The Federal

Highway Administration (FHWA) estimates that

megaregions will comprise 75% of the United States’

population by 2050 (Martin et al., 2016). For

policymakers, the challenge with megaregions is that the

areas are larger than the jurisdiction of metropolitan

planning organizations (MPOs) and generally span

multiple states.

ROLE OF TELEWORK AND TELECOMMUTING

Telecommuting is a work arrangement where employees

do not commute to a workplace (i.e., an office building)

and instead work remotely from an alternative location

(e.g., home, café, library, or other public or shared

workspaces) (Shaheen and Cohen, 2018b).

Telecommuting frequency (i.e., working remotely

intermittently or regularly) and location (i.e., working from

home or elsewhere) can vary. However, documenting

the impacts of telecommuting policies on travel behavior

is empirically difficult to measure and compare because

employers often do not monitor or survey their

employees (Nilles, 1988; Mokhtarian, 1991).

American Community Survey (ACS) data indicate that

there has been an increase in the share of people

commuting via telework between 2005 and 2013 based

FIGURE 2.1 MEGAREGIONS IN THE UNITED STATES

Source: America 2050


on US Census Journey to Work data. While studies on

the impacts of telecommuting on carpooling are limited,

anecdotal evidence suggests that the growth of part-time

telecommuting coupled with variable and non-traditional

employee work schedules, support the growth of flexible

and on-demand carpooling over traditional ridematching

approaches, which emphasize pairing employees for

carpooling trips on a regular and ongoing basis.

ATTITUDES TOWARD DRIVING

There is some evidence to suggest that attitudes among

Americans toward driving could be changing (Shaheen

and Cohen, 2018b). Handy et al. (2005) conclude that

Americans may be driving out of necessity due to limited

modal choices, urban sprawl, and the value proposition

of driving (travel time and flexibility compared to other

modal options). Millennials (those born between 1981

and 1996) are now the largest age group in the United

States and are often cited as the generation beginning to

reject car ownership. The percentage of high school

seniors with driver’s licenses decreased from 85% to

73% between 1996 and 2010 (Dutzik et al., 2014).

However, more research is needed to determine, if

Millennials have different attitudes and perceptions

toward auto ownership or are becoming “late” car

owners due to other factors, such as the Great

Recession, living at home longer and starting families

later in life than prior generations.

MILLENNIALS AND MOBILITY

One early study of Millennials and mobility concluded

that Millennial car owners are living downtown, are

parents of kids under 18, and are using cars as one

mode in a mix of options. The study also found that the

public transit industry may have an opportunity to better

promote the use of public transit and other transportation

options to Millennials in conjunction with driving. The

study also found that Millennials are motivated by cost,

reliability, convenience, and active lifestyles with

environmental considerations as an added perk. The

study also found that the ability to multi-task while

commuting is a key motivator when selecting


It is widely accepted that Millennials are embracing

information and communication technology (ICT), which

contributes to growth in mobile Internet connectivity, the

growth of smartphone apps, and wearable devices

among this cohort. However, research about the impact

of ICT on travel behavior is limited (Dutzik et al., 2014).

Another study by Blumenberg et al. (2012) found no

correlation between ICT usage and a reduction of driving

among Millennials. Mans et al. (2012) concluded it will

be difficult to model the impacts of ICT due to the many

and complex ways ICT could impact traveler behavior

(e.g., an online purchase may replace a shopping trip

with a delivery trip or create induced demand). However,

both the ability to multi-task while commuting coupled

with the attraction of ICT and app-based services

suggest that app-based carpooling could be an attractive

travel option for Millennials.

One trend not commonly discussed is the rising average

age of first marriage. Since 1970, the average age of first

marriage has steadily risen from 23.2 and 20.8 for men

and women, respectively compared to 29.2 and 27.1 in

2015 for men and women, respectively (Figure 2.2). This

indicator suggests that Millennials are delaying life

FIGURE 2.2 ESTIMATED MEDIAN AGE OF FIRST MARRIAGE BY GENDER: 1970 TO 2015

Source: U.S. Census Bureau, 2016


milestones, such as getting married and having children,

which could impact overall mobility decisions (e.g.,

modal choice and vehicle ownership).

Early indicators suggest Millennials could be purchasing

single family suburban homes similar to Generation X

and the Baby Boomers. A recent study of Millennials and

home ownership found that many Millennials are

bypassing the starter-home market in favor of a more

expensive “forever home” (Davidson, 2018). The study

concluded that by renting or living with their parents for

years, many Millennials in their mid-30s can now afford

pricier houses because they have saved more money

and moved up to better jobs. According to recent

statistics from the National Association of Realtors, 30%

of Millennials bought homes priced at $300,000 USD or

above this year, up from 14% in 2013 (Davidson, 2018).

Additionally, the U.S. Census Bureau found that almost a

third of home buyers aged 33 to 37 purchased four-

bedroom homes from 2012 to 2016, compared to about

24% in 1980, 1990, and 2000. If Millennials suburbanize

as they marry and have children, there could be renewed

interest in carpooling among this generational group.

MILLENNIALS MAY CONTINUE TO

SUBURBANIZE AS THEY RECOVER FROM THE

GREAT RECESSION AND ATTAIN LIFE

MILESTONES, SUCH AS GETTING MARRIED

AND HAVING CHILDREN.

SUBURBANIZATION

Contrary to popular belief that urban centers are growing

faster than the suburbs, the U.S. population is still

suburbanizing (Martin et al., 2016; Shaheen and Cohen,

2018b). More than eight in 10 Americans live in

metropolitan areas. Sixty-five percent live in large

metropolitan areas with over a half million people. Forty-

five percent of the U.S. population resides in the suburbs

of these large metropolitan areas, and 75% of U.S.

households reside in single-family or mobile homes

(Frey, 2012).

BETWEEN 1990 TO 2010, SUBURBS GENERALLY

GREW FASTER THAN URBAN CORES.

Recent studies indicate that America continues to

become more suburban. In the nation’s largest

metropolitan regions, seven in 10 residents now live in

the suburbs. Within each U.S. region, the suburban

portion of the population continued to rise in the 2000s

(Frey, 2012). Over this decade, suburban growth

exceeded urban growth in 81 of the largest 100 U.S.

metros.

Additionally, job centers are growing outside of urban

cores and in various suburban nodes, such as “edge

cities” (suburbs with high concentrations of employment

density, such as office parks) (Kneebone, 2016). This

study found that employment notably decentralized

between 1996 and 2006 with 95 out of 98 metro areas

decreasing the share of jobs located within three miles of

downtown. Kneebone (2016) concluded that only 21% of

employees in the top 98 metro areas work were within

three miles of downtown, while over twice that share

(45%) worked more than 10 miles away from the city

center. Because of more limited transportation options in

many suburbs, anecdotal evidence suggests that

carpooling can enhance suburban mobility by offering

additional transportation choices in a relatively auto-

dependent built environment.

FIGURE 2.3 FIVE COMMON BUILT ENVIRONMENTS IN THE U.S.

Source: Shaheen et al. 2017


SUMMARY

Many technological changes and demographics trends

are contributing to the growth of shared and on-demand

mobility, such as app-based carpooling. Key trends

include:

▪ Increasing availability of location-based mobile services;

▪ Growth and commodification of on-demand passenger travel;

▪ Increasing urban congestion;

▪ Growth of megaregions;

▪ Demographic shifts, such as rising life expectancies, an aging population, and Millennials delaying life milestones, such as marriage;

▪ A growing number of telecommuters;

▪ Potential changing attitudes toward driving and vehicle ownership; and

▪ Continued growth and expansion of many suburbs.

While longer-term attitudes toward driving and

suburbanization are less definitive, the need for

transportation solutions that reduce traveler stress,

overcome congestion, and increase overall

commuter productivity are clear. In the future, these

trends could create new demand for carpooling and

provide additional mobility options for new potential

carpoolers.


3

HOW GOVERNMENT AND

EMPLOYERS CAN SUPPORT

CARPOOLING


HOW GOVERNMENT AND EMPLOYERS

CAN SUPPORT CARPOOLING

A variety of stakeholders play a crucial role in supporting

carpooling. One of the most important methods

employers, local and regional governments, state

agencies, and the federal government can employ to

support carpooling is incentives. Employers and public

agencies at all levels of government can also support

carpooling in a variety of ways, ranging from specific

programs at the employer and local government level to

broader policy support at the state and federal levels of

government. Each of the following sections discuss ways

in which key stakeholders can support carpooling.

ROLE OF INCENTIVES AND DISINCENTIVES

Carpool incentive programs may incorporate a variety of

means to encourage employees to carpool. Common

incentives include direct cash incentives, reduced cost or

free parking, preferred parking, or reward programs

(such as prize drawings) (U.S. Environmental Protection

Agency, 2005).

A number of studies have tried to document the role of

incentives and disincentives. A study by Shoup (1997b)

found that parking cash out programs where employers

are required to give their employees a choice to either

keep their employer-paid parking space at work or to

accept a cash payment and give up the parking space,

increased carpooling by 64%, while decreasing single

occupant vehicle (SOV)-travel by 17%.

A study of Georgia’s Cash for Commuters program in

which new carpoolers were offered a $3 USD per day

incentive for 90-days to try carpooling found that 57%

continued to carpool 18 to 21 months after the initial

incentive period (Georgia Department of Transportation

2009). This study highlights the role that short-term

incentives can have in encouraging longer-term modal

shift.

Additionally, multiple studies have examined the impacts

of additional fees on solo driving with varied findings.

Jacobson and King (2009) found that if driving costs of

$1 USD are added to each vehicle trip, the maximum

rational value of time for travelers to choose ridesharing

approximately doubles. However, Baldassare et al.

(1998) and Koppelman et al. (1993) found that few

drivers are willing to reduce single occupant travel as a

result of pricing. In particular, Koppelman et al. (1993)

found that solo drivers were more likely to be influenced

to carpool through an incentive (e.g., weekly lotteries for

supermarket and movie vouchers) than by increases in

driving costs (e.g., parking, fuel, etc.).

EMPLOYER SUPPORT

Employers can enjoy several benefits from carpooling.

Common employer benefits include: 1) reducing parking

demand (to lower parking costs or to make a parking

space available for facility expansion); 2) reducing

congestion; 3) satisfying local zoning or air pollution

requirements; and 4) increasing employee productivity

and morale by reducing commute costs, time, and

stress.

Employers looking to encourage carpooling can draw

upon a number of strategies to encourage shared rides

and discourage SOV commutes. Employer support for

carpooling commonly includes a combination of

administrative support and financial support strategies:

Administrative Support Strategies:

▪ Providing tools that make it easier for employees

to find a match, such as commute planning

resources and matching or referral services to

help employees locate others nearby with similar

schedules;

▪ Offering marketing and outreach to encourage

carpooling; and

▪ Committing in-kind administrative support or

direct funding contributions to carpool programs.

Financial Support Strategies:

▪ Allowing parking cash out programs where an

employer offers employees the option to accept

taxable cash income instead of a free or

subsidized parking space at work (Shoup,

1997b);

▪ Implementing 100% commuter choice where

employers provide all employees an equal tax-

free transportation allowance equal to or less

than what an employer charges for parking (Lew

Pratsch, unpublished paper, 2017).

▪ Implementing carpool incentive programs that

incorporate a variety of strategies to encourage

employees to carpool. Common incentives

include: preferred parking for carpoolers; parking

cash-out programs;100% commuter choice;

discounted parking for carpools (if it is paid); and

reward programs, such as prize drawings.

▪ Leveraging gamification (e.g., the use of game

design elements in a non-game context) to

encourage carpooling competition among fellow

employees.

▪ Providing services that make carpooling more

convenient, such as public transit passes and

guaranteed ride home programs.


▪ Renting cars for carpools (similar to renting vans

for vanpools) to provide an option for two to five

passengers who want to carpool but may not

have a suitable vehicle.

A number of studies in the 1990s documented the cost

effectiveness of transportation demand management

(TDM) approaches for reducing vehicle travel and

emissions (Kuzmyak et al., 2010). Schreffler (1996)

found that the annual cost per an employee ranged from

$8 to $57 USD with an average of $24 USD (Schreffler,

1996). A 1993 Federal Highway Administration report

sampling 22 employer programs found the direct cost

per daily one-way vehicle trip reduced averaged $1.22

USD compared to an average cost savings of

$1.94 USD per trip reduced (Comsis Corporation, 1993).

Studies on the effectiveness of individual employer

carpooling programs are more limited. One study in the

Cornell University implementation of a carpooling

program in the 1990s found that the TDM program

succeeded in reducing the need to construct additional

parking spaces. Cornell University increased its parking

fees to disincentivize single occupant vehicles. The

university estimates its commuter benefits program

results in 2,400 fewer daily vehicle trips and a savings of

$36 million USD during the first ten years of program

implementation (U.S. Environmental Protection Agency

2005).

Collectively these studies found that employer TDM

programs that incorporate financial incentives and

disincentives are generally the most effective in reducing

vehicle trips and have the lowest cost per employee and

per trip reduced (Kuzmyak et al., 2010).

LOCAL AND REGIONAL SUPPORT

Local and regional governments can support carpooling

in a number of ways. First, local and regional

governments can partner with private sector employers

and carpooling providers to support local and regional

ridematching efforts. Additionally, they can provide

incentives and sponsor guaranteed ride home programs

for carpooling. In addition to these policies, local and

regional governments can:

▪ Implement parking reforms, such as pricing

parking, eliminating parking minimums,

instituting 100% commuter choice, and

implementing parking cash-out programs;

▪ Institute road and curb pricing strategies, such

as road tolls, congestion fees, and other

charges;

▪ Implement trip reduction and TDM ordinances;

and

▪ Fund carpooling infrastructure and support high

occupancy vehicle priority through HOV lanes,

park-and-ride facilities, encourage the inclusion

of carpooling parking at new and existing

facilities, and implement signal prioritization for

higher occupancy vehicles.

Each of these topics are discussed in greater detail

below.

PARKING: ZONING, PRICING, 100%

COMMUTER CHOICE, AND PARKING CASH-

OUT

In most U.S. cities, parking is typically free. The

oversupply of free parking can distort the transportation

marketplace and individual mode choice. Many cities

have implemented minimum parking requirements

requiring new buildings to include a fixed number of off-

street parking spaces based on an assumed demand for

parking generated by the buildings' use (Shoup, 2011). A

common criticism of minimum parking requirements is

that they assume a building’s users will travel by car

providing a one-size fits all approach mandating parking

supply, often requiring sufficient supply for a building’s

peak (e.g., minimum parking at a shopping center based

on the number of shoppers during the holiday season).

Minimum parking requirements are often attributed to an

over supply of underpriced parking subsidizes low-

occupancy private vehicle use (Shoup, 2005).

Nationally, employers provide 85 million free parking

spaces for commuters (Shoup and Breinholt, 1997).

Typically, the capital costs of parking range from

approximately $10,000 to $75,000 USD per parking

space (surface versus structured parking, respectively)

and $300 to $700 USD for operations and maintenance

per parking space annually. With minimum parking

requirements, cities require developers to increase

parking supply by as much as a new development

increases parking demand assuming that the parking is

free (Shoup, 2011). As such, minimum parking

requirements provide subsidies for driving that inflate

parking demand. By severing the cost of providing

parking and the price drivers pay for it, the true cost of

parking is not passed onto the driver and therefore fails

to influence travel decisions about vehicle ownership and

use (Shoup, 2011).

Shoup (1995) found that when commuters paid for

parking, they drove an average of 53 vehicles to work

per 100 employees. However, when commuters parked

free, they drove an average of 72 cars per 100


employees, stimulating a 36% increase in the number of

cars driven to work (Shoup, 1995).

Eliminating minimum parking requirements and pricing

existing parking are two strategies that can reduce

oversupplies of parking and single occupant vehicle use.

If parking were less plentiful and priced, people would be

more prudent about when and where they drove (Shoup,

2011).

Another strategy, 100% commuter choice involves

employers providing all employees an equal tax-free

transportation allowance equal to or less than what an

employer charges for parking. If a commuter needs to

drive alone to work, they use the 100% commuter choice

allowance provided by the employer to pay for parking.

Other employees might choose to move closer to work

walk, use public transit, cycle, carpool, or vanpool to

work (Lew Pratsch, unpublished paper, 2017). Studies

show that 10-20% of the commuters who drive alone to

work and park free would choose another mode if

required to pay for parking. A FHWA report documents a

10-15% decrease in VMT can reduce traffic congestion

over 50% (Louis Berger Group, Inc 2008; Lew Pratsch,

unpublished paper, 2017).

Finally, parking cash-out, can also reduce single

occupant vehicle travel. Parking cash-out, which can be

implemented by employers or through local or state

mandates, is an employer-funded program in which an

employer offers a cash allowance to an employee

equivalent to the parking subsidy that an employer would

otherwise pay to provide the employee with a parking

space. For example, in 1992 California enacted

legislation that converted employer-paid parking from a

matching grant for driving to a block grant for commuting

(Shoup, 1997a). The law requires employers that

subsidize commuter parking to offer a parking cash-out

program. Although implemented on a statewide scale,

parking cash-out can be required by local and regional

governments or voluntarily offered by individual

employers. By offering commuters the option to elect

free parking or its cash value makes it clear that free

parking has a cost. Parking cash-out can encourage

commuters that drive to work alone and park for free to

carpool.

ROAD AND CURB PRICING

In addition to pricing parking, road and curb pricing are

also strategies that can encourage higher occupancy

modes (Forscher et al., 2018). Road and curb pricing are

direct charges that are levied for the use of roads and

curb frontage, such as road tolls, distance or time-based

fees, congestion charges, and fees designed to

discourage certain vehicles or behaviors, such as higher

polluting vehicles and lower occupancy vehicles,

respectively.

In the context of pooling, pricing can be applied to

discourage single occupant vehicle travel. For example,

in the San Francisco Bay Area, the Bay Area Toll

Authority responsible for administering regional bridge

tolls provides discounts for carpools during commute

times (Bay Area Toll Authority, 2018). Toll discounts for

carpoolers vary from approximately 30% to 60%

depending on the bridge and if electronic toll collection is

used (Bay Area Toll Authority, 2018).

FIGURE 3.1 BAY AREA TOLL AUTHORITY RATES FOR

SINGLE-OCCUPANT AND CARPOOL VEHICLES

Source: Bay Area Toll Authority 2018

In addition to road pricing, pricing can also be used to

manage curb space demand. Charging pricing based on

vehicle occupancy is one way to discourage lower

occupancy vehicles and encourage carpooling in urban

centers (Goffman, 2018). Pricing curb access for lower

occupancy vehicles can reduce the amount of curb

space needed to meet demand, reduce total vehicle

traffic, and increase revenue.

In an automated future, road and curb pricing will be an

important component in mitigating some of the potential

negative externalities of automated vehicles on

congestion, the environment, and equity (Stocker and

Shaheen, 2018; Moavenzadeh and Lang, 2018). If

automated vehicles (privately owned and shared) are

appropriately priced based on their usage, higher-

occupancy transportation modes, such as carpooling

(Shaheen and Cohen, 2018a), may become more

attractive and gain higher ridership than would be the

case absent of any road pricing regulations. A simulation

by Moavenzadeh and Lang (2018) estimates a 15.5%

travel time improvement attributable to road pricing in an

automated future (Moavenzadeh and Lang, 2018). A

combination of pooling incentives with various pricing

policies and rights-of-way access policies, tailored to city


and regional travel patterns, will be necessary to mitigate

the potential negative impacts of an automated vehicle

future (Stocker and Shaheen, 2018).

TRIP REDUCTION AND TRANSPORTATION

DEMAND MANAGEMENT (TDM) ORDINANCES

Local and regional support for carpooling can also

include establishing TDM or trip reduction ordinances.

These policy approaches offer a combination of “carrot”

and “stick” approaches that require a reduction in single

occupant vehicle trips, while also encouraging the

inclusion of carpooling into residential, commercial, and

mixed-use projects.

Air quality districts failing to meet federal standards

began implementing these ordinances in the 1980s. One

of the largest mandated trip reduction programs was

implemented in 1988 by the South Coast Air Quality

Management District (SCAQMD) requiring employers to

meet a minimum average vehicle ridership (AVR) of 1.5

for most of the urbanized region (Dill, 1998). AVR is the

current number of employees scheduled to report to

work during a given timespan (i.e., the morning

commute) divided by the number of vehicles arriving at

the worksite during the same window. When the

regulation was implemented, the trip reduction mandate

affected over 2.26 million employees or 40% of

SCAQMD’s 5.4 million workers (Giuliano et al., 1993;

Dill, 1998). This regulation has since been amended,

establishing varying AVRs ranging from 1.3 to 1.75

based on one of three zones.

Seattle’s Municipal Code requires that employers

implement at least two trip reduction programs, which

can include ridematching services for employees,

subsidies for carpool participation, and preferential

parking and reduced parking fees for carpool and

vanpool vehicles. The Seattle Department of

Transportation (SDOT) estimates over 250 employers

with over 139,000 daily commuters participate in the

city’s trip reduction program. SDOT estimates that its

program has contributed to an 11% reduction in single

occupant vehicle (SOV) trips with an additional 10%

estimated for 2017 (results are currently being

tabulated). A number of other Washington municipalities

have implemented trip reduction programs, including

some paired with monetary incentives. The City of

Redmond offers a monthly gift card lottery for taking

alternative modes at least four days per month and the

City of Bellevue offers a perks program where

commuters can earn monthly coupons to local retailers

and be entered to win one of 25 monthly gift card

drawings.

Like Washington, numerous Arizona localities have

implemented similar trip reduction ordinances. For

example, Maricopa County (Phoenix metro) requires

major employers with 50 or more employees to

implement eligible trip reduction measures including but

not limited to ridematching services, carpooling

subsidies, and preferential parking for carpooling. In

2011, 2,993 Maricopa County employers participated in

the local Trip Reduction Program. Similarly, Pima County

(Tucson metro) has also implemented a trip reduction

ordinance similar to the Arizona and Washington laws.

Pima County’s law requires major employers with 100 or

more employees to implement eligible trip reduction

measures, such as ridematching services, carpooling

subsidies, and preferential carpooling parking.

In addition to mandating trip reductions, local and

regional governments can implement policies that

encourage carpooling by integrating provisions within

building codes. For example, in April 2016, the City of

Indianapolis revised its zoning and subdivisions

ordinance to permit developers a cumulative reduction in

required parking up to 35% for the inclusion of TDM

measures. One of the measures that help developers

qualify for this parking reduction is the inclusion of

carpool and vanpool parking spaces. Indianapolis allows

developers to reduce off-street parking by four spaces

for each carpooling parking spot in addition to allowing

each carpool parking spot to count toward the minimum

number of required spaces.

In summary, trip reduction and transportation demand

management ordinances can be implemented by local

and regional public and quasi-public agencies (e.g.,

MPOs, air quality districts, cities, etc.). Implementation of

trip reduction and demand management ordinances vary

widely and can include imposing AVR standards,

implementing employer programs (e.g., preferential

parking for carpools, monetary incentives, etc.), and

minimum parking reduction incentives for developers.

Table 3.1 summarizes examples from a selection of local

governments across the U.S.


TABLE 3.1 EXAMPLES OF LOCAL TRIP REDUCTION AND

TRANSPORTATION DEMAND MANAGEMENT ORDINANCES

Jurisdiction Key Policy Components

Bellevue, WA • Key Component: Earned Incentives and Lotteries

• Applicability: Commuters can earn coupons and enter drawings for additional rewards

Indianapolis, IN • Key Component: Minimum parking reductions for developers for the inclusion of carpooling and other infrastructure supportive of alternative modes

• Applicability: Developers can earn a 35% cumulative minimum parking reduction for the inclusion of TDM measures, such as carpooling parking in a new development

Maricopa County, AZ • Key Component: Mandated employer commute trip reduction program

• Applicability: Employers with 50 or more employees are required to implement trip reduction measures, such as ridematching, carpooling subsidies, and preferential parking for carpooling

Pima County, AZ • Key Component: Mandated employer commute trip reduction program


Redmond, WA • Key Component: Lotteries

• Applicability: Commuters taking alternative modes can enter a lottery for gift cards

Seattle, WA • Key Component: Mandated employer commute trip reduction program


South Coast Air Quality Management District (SCAQMD)

• Key Component: Average vehicle ridership (AVR)

• Applicability: Worksites with 250 or more employees must implement an annual commute trip reduction program that that achieves an average vehicle ridership performance requirement of 1.3 to 1.75 depending on the geographic zone

CARPOOLING INFRASTRUCTURE AND HIGH

OCCUPANCY VEHICLE (HOV) PRIORITY

A number of carpooling infrastructure and priority

policies can be implemented individually or collectively to

provide priority to higher occupancy vehicles, such as

carpools. Carpooling infrastructure typically includes:

▪ High occupancy vehicle (HOV) highway and

arterial lanes that provide carpoolers a network

of HOV lanes on highways and high-volume

corridors and surface streets; and

▪ Park-and-ride facilities that provide parking for

travelers to leave their vehicles and transfer to a

carpool or public transportation for the remainder

of their journey.

The availability of HOV lanes and park-and-ride facilities

are a critical component of promoting carpooling within a

region. A study in the San Francisco Bay Area found that

59% of park-and-ride commuters formed prearranged

and casual carpools at facilities that were near HOV

lanes or inadequately served by public transit

(Shirgaokar and Deakin, 2005). Turnbull et al. (2006)

found that HOV lanes are most effective at reducing

single occupant vehicle use on congested highways to

large employment centers in large urban areas with high

frequency bus service during peak periods, where public

transit provides time savings of at least five to 10

minutes per trip (Victoria Transport Policy Institute 2014).

Turnbull (2001) provides implementation guidelines for

HOV facilities emphasizing effectiveness in major urban

areas with large employment centers, heavy congestion,

and supportive TDM policies. Best practices for

implementing effective HOV facilities include:

▪ A minimum threshold of approximately one

million people in a metropolitan region;

▪ High levels of traffic congestion along a corridor;

▪ Access to an employment center with more than

100,000 workers;

▪ Supportive TDM programs and policies with

ongoing marketing;

▪ Visible HOV or automated HOV enforcement;

and

▪ Institutional, local, and regional support for

carpooling.

HOV lanes can be implemented by adding new road

capacity designated for HOVs or converting an existing

lane to HOV use. HOV lanes have a number of varying

design and operational characteristics, such as:

▪ Separation from regular traffic using signs,

markings, painted buffers, or physical barriers;

and

▪ Operational hours varying from peak hours only

to 24 hours. Some facilities may use reversible

lanes for areas with high levels of directional

traffic.

Studies indicate that HOV lanes can reduce vehicle trips

by 4% to 30% (Comsis Corporation, 1993; Turnbull et al.

2006; Victoria Transport Policy Institute 2014). Another

study estimates that HOV lanes can reduce peak period

vehicle trips by two to 10%, and up to 30% on congested

corridors, if HOV lanes are separated by a barrier

(Ewing, 1986). Apogee (1994) concluded that HOV lanes

can regionally reduce VMT by 1.4% and vehicle trips up

to 0.6% (Victoria Transport Policy Institute 2014).


HOV FACILITIES ARE MOST APPROPRIATE ON

CONGESTED HIGHWAYS WHERE HOV USE CAN

RESULT IN NOTABLE TRAVEL TIME SAVINGS

FOR CARPOOLERS.

Park-and-ride facilities are parking lots that allow

commuters to park their vehicles and carpool or take

public transit to their destination. Park-and-ride facilities

are typically located in the suburbs or outskirts of

metropolitan areas (Turnbull et al., 2004). The average

park-and-ride typically contains between 30 and 250

parking spaces; however, some facilities can have more

than 2,000 parking spaces.

While research on the impacts of park-and-ride lots are

limited, anecdotal evidence indicates that these facilities

support carpooling because they provide a safe,

convenient meeting location for travelers to form a

match. Studies suggest that one carpool is formed for

approximately every 1.5 vehicles parking in these

facilities (Turnbull et al., 2004; Victoria Transport Policy

Institute 2014). Additionally, these facilities can shift

parking and congestion out of existing urban areas to

lower density, less congested areas (Turnbull et al.,

2004; Victoria Transport Policy Institute 2014).

In addition to HOV lanes and park-and-ride facilities, a

number of policies can prioritize carpooling and

encourage sharing a ride through travel time savings.

These policies include:

▪ Queue jumping where HOV lanes can by-pass

ramp metering and enter immediately, while

SOV lanes must wait for the ramp meters;

▪ Signal prioritization for HOV lanes on surface

streets; and

▪ Preferred parking space locations or parking fee

discounts for carpooling vehicles.

Each of these policies can help reduce travel times for

higher occupancy vehicles. HOV priority effectiveness

will typically depend on maintaining notable travel time

savings over single occupant vehicle trips. As such, this

policy should target corridors with congested general

purpose lanes where maximum travel time savings could

be achieved (Victoria Transport Policy Institute 2014).

In summary, signal prioritization for HOVs, HOV ramp

metering priority, a network of HOV lanes, park-and-ride

facilities, and preferred parking for carpooling can create

a synergy that supports and encourages carpooling

usage.

STATE AND FEDERAL SUPPORT

The state and federal levels of government can support

carpooling in a number of ways. Three key ways that

state and federal agencies can support carpooling

include:

▪ State and federal agencies can provide tax

incentives and commuter tax benefits for

carpooling;

▪ State and federal agencies can implement clear,

concise carpooling definitions;

▪ State and federal agencies could implement

performance-based contracts that allow

contractors to receive performance bonuses for

verifiable reductions in traffic or VMT (Lew

Pratsch, unpublished paper, 2017); and

▪ State agencies can implement statewide trip

reduction laws (similar to local trip reduction

ordinances).

Each of these support strategies are discussed in

greater detail below.

TAX INCENTIVES AND COMMUTER TAX

BENEFITS FOR CARPOOLING

Section 132(f) of the U.S. Internal Revenue Code

provides a way for employers to provide parking, public

transit, vanpool, and bicycle expenses on a tax-free

basis. This can be done on a pre-tax basis, through

employer subsidies, or both of these approaches.

▪ With pre-tax public transit benefits, employees

can elect to withhold funding from their

paycheck. Those funds are used to purchase

fares for public transit or vanpools. The

employee is not taxed on the funding withheld,

and the employer does not pay employment

taxes on those funds.

▪ Through subsidies, employers can provide

public transit or vanpool fares in addition to

salary. With subsidies, neither the employee is

not taxed on the value of these funds nor does

the employer pay employment taxes on those

funds.

▪ Employers can subsidize a portion of an

employee’s commute expenses, and the

employee can withhold an additional amount

based on need on a pre-tax basis (Internal

Revenue Service, 2018).

Previously, employers could deduct the subsidy portion

of a commuter’s expenses that were paid for by the

employer. This tax benefit was eliminated with the


passage of the Tax Cuts and Jobs Act of 2017. While

employers can still subsidize these expenses, employers

can no longer deduct the subsidized portion of their

commuters’ expenses (WageWorks, 2018).

THE FEDERAL GOVERNMENT COULD EXPAND

SUPPORT FOR CARPOOLING BY EXPANDING

SECTION 132(F) OF THE INTERNAL REVENUE

CODE TO INCLUDE CARPOOLING AND

SIMPLIFYING THE TAX CODE.

Historically, there have been ambiguities in the IRS tax

code pertaining to cash reimbursements received by

carpool and vanpool drivers. Cash reimbursements

received by carpool and vanpool drivers are difficult to

track due to the cash nature and size of the transactions.

The federal government could expand its support for

carpooling by simplifying the tax code by exempting

reimbursements received by drivers of commuter driven

vehicles carrying up to 15 commuters from taxable

income and making them ineligible as business

deductions (Lew Pratsch, unpublished paper, 2017).

This would simplify the tax code, eliminate difficult to

enforce regulations, and negate the need for carpool and

vanpool drivers to keep tedious records (Lew Pratsch,


A number of states have implemented tax incentives and

commuter tax benefits for carpooling. For example,

Maryland offers an employer tax credit of 50% of the

eligible costs of providing commuter benefits to

employees. The tax credit is applicable to an array of

commuting expenses, including vanpooling, guaranteed

ride home, and parking cash-out programs (Comptroller

of Maryland, 2018). The State of Washington offers a

Commute Trip Reduction Tax Credit for all employers

and property managers “who are taxable and provide

financial incentives to their employees for ridesharing,

carsharing, public transportation, and non-motorized

commuting.” This credit is valued at up to $60 USD per

employee per a fiscal year, up to $100,000 USD per an

employer/property manager annually (Revised Code of

Washington 82.70.010 et seq.). Georgia offers a similar

tax credit of $25 USD for each employee that uses a

federal qualified transportation fringe benefit at least 10

days per a month. This credit is available to employers

that provide carpool or vanpool parking on or near the

workplace (Georgia Code 48-7-29.3 et seq.).

In summary, tax incentives and commuter tax benefits

for carpooling are a key way the federal and state

government can support carpooling. Table 3.2 compares

key tax incentives and commuter tax benefits from the

states of Maryland, Georgia, and Washington.

TABLE 3.2 EXAMPLES OF STATE-LEVEL TAX INCENTIVES

AND CREDITS FOR CARPOOLING

State Incentive Beneficiary

Incentive Amount

Maryland Employer 50% of the eligible costs of providing commuter benefits to employees.

Georgia Employer $25 for each employee using a federal qualified transportation fringe benefit at least 10 days per a month.

Washington Employer and Property

Managers

$60 per employee per a year, up to $100,000 per an employer/property manager annually

CLEAR AND CONCISE DEFINITIONS OF

CARPOOLING

Increasingly, differing terms and definitions can be

confusing for the public and policymakers. Developing

clear, consistent, and precise definitions can encourage

the growth of carpooling by providing policy and

decisionmakers with a greater understanding of the

types of pooled services available and their associated

impacts (Shaheen et al. 2016). Clear and consistent

definitions can help to clear confusion about modes and

service models.

As noted by SAE International, a global standards

organization for mobility engineering, certain terms such

as “ridesharing” are sometimes used inconsistently or

confusingly. SAE Standard J3163, states “a for-hire

vehicle service with one paid driver and one paid

passenger is not considered ridesharing (or carpooling).

While some ridesourcing services offer shared rides for

more than one traveler, these services are referred to as

“ridesplitting,” “pooling,” and “taxi sharing,” the latter

used to describe sharing a taxi cab (SAE International

2018).

PERFORMANCE-BASED CONTRACTS FOR

CONGESTION MITIGATION

State and federal agencies could implement

performance-based contracts for congestion mitigation

(Lew Pratsch, unpublished paper, 2017). The FAST Act

and MAP-21 encourage performance and outcome-

based programs to achieve reductions in congestion and

improvements in system reliability of the transportation

network. One strategy for reducing congestion is for

state and federal agencies (perhaps through Congestion

Mitigation and Air Quality (CMAQ) funds) to initiate

performance-based contracts that provide contractors

performance bonuses that reduce traffic or VMT.

Contractors could develop plans to decrease traffic

congestion, develop a verification procedure, and upon


successfully demonstrating performance, be awarded a

contract bonus for congestion reduction. Incentives could

be based on a portion of the annualized cost of adding

additional roadway capacity along a congested corridor

or urban area. Measures could include carpool

marketing, the use of apps that reduce congestion,

conversion of HOV lanes to high occupancy toll (HOT)

lanes, HOV/HOT lane additions, parking and congestion

pricing, and other initiatives (Lew Pratsch, unpublished

paper, 2017).

STATEWIDE TRIP REDUCTION LAWS

Similar to local trip reduction ordinances, states can pass

legislation or issue regulatory mandates requiring

commute trip reduction benchmarks. For example, the

State of Washington has implemented a state-wide

Commute Trip Reduction Law applying to all employers

with 100 or more full-time employees at a single worksite

who are scheduled to begin their workdays between 6:00

and 9:00 a.m. weekdays and are located in counties or

urban growth areas with populations exceeding 150,000.

As part of this law, employers are required to develop

their own trip reduction plans and submit them for

approval (Washington Code 468-63-010 et seq.; Revised

Code of Washington 70.94.521 et seq.) (Interagency

Commute Trip Reduction Board 2011). Many local

municipalities have adopted similar local ordinances

mimicking this state law. Similarly, Arizona State

requires all major employers to develop, implement, and

maintain a travel reduction program to reduce traffic

impacts on air pollution and emissions (Arizona Code

49-581 et seq.).

In Massachusetts, the Department of Environmental

Protection (MassDEP) has implemented a statewide

ridesharing regulation that requires facilities to develop

plans and set goals for reducing employee and student

drive-alone commute trips by 25%. This regulation

applies to business that employ 250 or more daytime

employees and educational institutions with 1,000 or

more applicable commuters. MassDEP’s regulation

requires facilities to conduct carpool matching using a

designated coordinator or using a carpool-matching

service and set aside preferential spaces for carpools

(Massachusetts Code 310 CMR 7.00 et seq.).

Similar to MassDEP, Oregon’s Department of

Environmental Quality has implemented an Employee

Commute Options Program requiring that employers with

more than 100 employees at a single worksite must

provide commute options to employees designed to

reduce the number of cars driven to work in Portland and

surrounding areas. These employers must provide

incentives for employee use of commute options, like

taking the bus or carpooling (Oregon Administrative

Rules 340-242-0010 et seq.).

Trip reduction laws are one common way state

governments encourage the implementation of

carpooling programs at the employer level. Table 3.3

summarizes state trip reduction laws in Arizona,

Massachusetts, Oregon, and Washington.

TABLE 3.3 EXAMPLES OF STATE TRIP REDUCTION LAWS

State Key Policy Components

Arizona • Requirements: Major employers must provide employees with information on alternative commute options, participate in a mode choice and VMT survey, designate a transportation coordinator, and implement trip reduction measures such as: providing ridematching and vanpooling services, subsidizing carpooling and vanpooling, allowing the usage of company vehicles for carpooling, and offering preferential parking for carpooling among other applicable measures

• Applicability: All major employers with 100 or more full-time employees (50 or more employees in select areas) working at or reporting to a single work site during any 24 hours period for at least three days per week during at least six months of the year

Massachusetts • Requirements: Facilities must offer carpool matching using a designated coordinator or carpool-matching service and set aside preferential spaces for carpools

• Applicability: Businesses that employ 250 or more daytime employees and educational institutions with 1,000 or more applicable commuters

Oregon • Requirements: Employers must offer commute options to employees designed to reduce single-occupant vehicle commute trips; incentives must have the potential to reduce commute trips by 10% from an established baseline

• Applicability: Employers with 100 or more employees at a single worksite

Washington • Requirements: Employers must develop their own trip reduction plans and submit them for approval

• Applicability: All employers with 100 or more full-time employees at a single worksite with a scheduled start between 6-9:00 AM on weekdays; employers located in urban growth areas or counties with populations exceeding 150,000


SUMMARY

Employers, local and regional governments, and the

federal government can play an important role in

supporting carpooling. The primary ways employers can

support carpooling include:

▪ Helping employees form carpools by providing

matching or referral services to help locate

matches with similar schedules;

▪ Providing tools that make carpooling more

convenient, such as commute planning

resources, public transit passes, and guaranteed

ride home programs; and

▪ Implementing 100% commuter choice, parking

cash-out, and other carpool incentive programs.

The primary ways local and regional governments can

encourage carpooling include:

▪ Partnering with private sector employers and

carpooling providers to support local and

regional ridematching efforts;

▪ Considering parking reforms, such as pricing

parking, eliminating parking minimums, and

implementing 100% commuter choice and

parking cash-out programs;

▪ Considering pricing policies that incentivize

higher occupancy and disincentivize low-

occupancy modes;

▪ Implementing trip reduction and TDM

ordinances; and

▪ Supporting HOV infrastructure (e.g., HOV lanes

and park-and-ride facilities) and signal

prioritization that encourages carpooling.

State and federal governments can support carpooling

by:

▪ Employing tax credits and commuter tax benefits

for carpooling. In particular, the federal

government can encourage carpooling by

expanding commuter tax benefits to carpooling

and simplifying the tax code pertaining to cash

reimbursements received by carpool and

vanpool drivers;

▪ Developing clear, concise, and consistent

definitions of carpooling;

▪ Implementing performance-based contracts for

contractors that successfully reduce congestion

(Lew Pratsch, unpublished paper, 2017); and

▪ Implementing state-level trip reduction laws.


4

CONCLUSION


KEY TAKEAWAYS

Carpooling allows travelers to share a ride to a common

destination and can include several forms of sharing a

ride, such as casual carpooling and real-time carpooling.

Today, carpooling is the second most common travel

mode in the United States after driving alone—although

percentages have continued to decline in recent

decades. More policy support is needed to reverse this

trend and increase carpooling mode share, particularly in

an automated vehicle future.

CARPOOLING IMPACTS AND MOTIVATORS

Carpooling is often associated with numerous societal,

employer, and individual benefits.

SOCIETAL BENEFITS

▪ Reduced vehicle miles traveled;

▪ Reductions in fuel consumption and GHG

emissions;

▪ Reductions in adverse air pollution impacts on

low-income, minority, and other environmental

justice populations; and

▪ Cost savings for public agencies and employers.

EMPLOYER BENEFITS

▪ Reduced need for parking;

▪ Increased morale and productivity of employees;

and

▪ Financial and tax benefits for employers.

INDIVIDUAL CARPOOLING BENEFITS AND

MOTIVATORS

▪ Enhanced accessibility and economic

opportunity for low-income households;

▪ Cost savings associated with shared travel

costs; and

▪ Increased convenience and reduced stress from

shared driving responsibilities and travel-time

savings associated with HOV lane access.


Socio-economic forces, coupled with technological

innovations, are encouraging shared and pooled

services. Key technological, mobility, social, and

demographic trends changing the way people travel

include:

TECHNOLOGICAL TRENDS

▪ Growth of cloud computing, location-based

navigation services, data sharing, and mobile

technologies; and

▪ Commodification of passenger services

supporting app-based and on-demand


MOBILITY TRENDS

▪ Increasing demand and urban congestion,

reduced transportation funding, and the critical

need to maximize existing infrastructure

capacity; and

▪ Growing popularity of shared and higher

occupancy modes, such as microtransit, app-

based carpooling, and others; and

▪ Increasing consumer interest in on-demand


SOCIAL TRENDS

▪ Heightened environmental awareness about

emissions and carbon footprint, and

▪ Growth of megaregions.

DEMOGRAPHIC TRENDS

▪ Demographic changes, such as rising life

expectancies, people working longer, and

Millennials entering the workforce;

▪ People delaying life milestones, such as getting

married and having children that could have an

impact on automobile ownership and use; and

▪ Millennials increasingly embracing apps and

other technologies.

OTHER TRENDS

▪ Growing number of telecommuters,

▪ Possible changing attitudes toward driving and vehicle ownership, and

▪ Continued growth and expansion of many suburbs.


HOW GOVERNMENT AND EMPLOYERS CAN

SUPPORT CARPOOLING

A variety of public and private stakeholders play a crucial

role in supporting carpooling. Below are key ways each

of these stakeholders can support carpooling.

EMPLOYER SUPPORT

Employers can support carpooling by:

▪ Allowing parking cash out programs and 100%

commuter choice (Shoup, 1997b; Lew Pratsch,


▪ Providing tools that make it easier for employees

to find a match, such as commute planning

resources and matching or referral services to

help employees locate others nearby with similar

schedules;

▪ Providing marketing and outreach to encourage

carpooling;

▪ Committing in-kind administrative support or

direct funding contributions to carpool programs;

▪ Implementing carpool incentive programs, such

as: reduced or free parking; preferred parking for

carpoolers; parking cash-out programs;

discounted parking for carpools (if it is paid); and

reward programs, such as prize drawings;

▪ Incorporating game design elements (e.g.,

gamification) to encourage carpooling

competition among fellow employees; and

▪ Providing services that make carpooling more

convenient, such as public transit passes and

guaranteed ride home programs.

LOCAL AND REGIONAL GOVERNMENT

SUPPORT

Local and regional governments can support carpooling

by:

▪ Implementing parking reforms, such as pricing

parking, eliminating parking minimums, and

implementing 100% commuter choice and

parking cash-out programs;

▪ Instituting road and curb pricing strategies, such

as road tolls, congestion fees, and other

charges;

▪ Implementing trip reduction TDM ordinances;

and

▪ Funding carpooling infrastructure and supporting

high occupancy vehicle priority through HOV

lanes, park-and-ride facilities, and other

measures, such as signal prioritization.

STATE AND FEDERAL GOVERNMENT

SUPPORT

States and the federal government can support

carpooling by:

▪ Providing tax incentives and commuter tax

benefits for carpooling;

▪ Simplifying the tax code by exempting

reimbursements received by drivers of

commuter driven vehicles carrying up to 15

commuters from taxable income and making

them ineligible as business deductions (Lew

Pratsch, unpublished paper, 2017);

▪ Implementing clear, concise carpooling

definitions;

▪ Implementing performance-based contracts for

contractors that successfully reduce congestion

(Lew Pratsch, unpublished paper, 2017); and

▪ Developing statewide trip reduction laws (similar

to local trip reduction ordinances).


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